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D-mannose is a natural sugar very similar to glucose. It reduces urinary tract infections and improves the symptoms of a rare metabolic genetic disorder. It may also act as a prebiotic and help with weight loss. Continue reading to learn more about D-mannose, its health benefits, and side effects.

What is D-Mannose?

D-mannose (occasionally known as carubinose, seminose, and mannopyranose) is a simple sugar that occurs naturally in the body. It’s also found in animals, plants, and microbes. Although it’s a close relative of glucose, D-mannose is much less efficient at storing energy [R, R].

D-mannose acts as a health-promoting “glyconutrient” in the body. It activates proteins by binding to them (creating so called “glycoconjugates”), which allows proteins to play out important roles in many tissues and organs [R, R].

Humans can take in d-mannose through diet or produce it from fructose. Most of the blood D-mannose that enters cells (98%) is transformed to the fruit sugar fructose. Fructose is broken down to release energy, while only ~2% is used to bind proteins. These proteins can release D-mannose back into the blood to maintain D-mannose levels [R, R, R].

One study associated high D-mannose levels with an increased risk of developing chronic disorders such as type 2 diabetes, heart disease, and kidney problems (albuminuria) [R].

Although high D-mannose levels are associated with advanced esophageal cancer, a study on 159 people with this cancer found that those with higher D-mannose levels had a lower risk of cancer recurrence and death [R].

Mechanisms of Action

UTIs

Most UTI infections are caused by E. coli, which attaches itself to the lining of the urinary tract by small hair-like proteins. D-mannose taken orally is excreted from the body by urine. While passing through the urinary tract, D-mannose clings to E. coli proteins and detaches the bacteria. As urine leaves the body, bacteria bound to D-mannose are flushed with it [R, R].

Genetic metabolic disorders

Congenital disorder of glycosylation type Ib is a rare genetic disorder caused by a defect in the enzyme that makes D-mannose from fructose (phosphomannose isomerase). People with this condition can’t bind D-mannose to proteins and suffer from liver damage, digestive and blood clotting abnormalities. Intake of D-mannose in high amounts raises its blood levels and ensures normal metabolism [R, R].

Uses & Benefits of D-Mannose

1) D-Mannose Reduces UTIs

What are UTIs?

UTIs are bladder infections that can affect any part of the urinary tract, including the urethra and kidneys. Most of them (75-90%) are caused by E. coli, which can enter the bladder through the urethra and begin to multiply [R, R+].

UTIs are much more common in women, half of which suffer from at least one in their lifetime. Women have a shorter urethra than men, making it easier for the bacteria to travel to the bladder. The main risk factors for developing UTIs in women are [R+]:

Being sexually active (risk increases with frequency of sexual intercourse)

Some birth control methods — diaphragms with spermicide more so than birth control pills [R]

Menopause

Pregnancy

Urinating after sex was linked to UTIs in women who previously didn’t experience them in one study, others found the opposite, while some studies did not find any link between urinating after sex and UTI risk. Maintaining good intimate hygeine seems to be more important [R, R, R].

UTIs can also affect men in rare cases. Factors that increase UTI risk in both men and women include age, weakening of the immune system, medical conditions such as diabetes or multiple sclerosis, and catheter use [R].

Although antibiotics can resolve UTIs, their long-term use may cause adverse effects and make the bacteria resistant. D-mannose is an important alternative therapy [R+, R+].

D-mannose for UTIs

In a clinical trial of over 300 women with recurrent UTIs, D-mannose (2g/day) for 6 months was as effective as the antibiotic nitrofurantoin at reducing UTI recurrence [R]

In another trial of 60 women, D-mannose was more effective than two other antibiotics (trimethoprim and sulfamethoxazole). It was used at a higher dose for 2 weeks (3g/day) and maintained at a lower dose for 6 months (1 g/day) [R].

D-mannose (3g/day) also reduced UTI recurrence in a clinical trial of 22 people with multiple sclerosis after 4 months [R].

In a clinical trial of 43 women with mild bladder inflammation, D-mannose resolved most symptoms and reduced their recurrence. It was given at 3g/day for 3 days followed by 1.5 g/day for 10 days [R].

Recurrent UTIs are a frequent cause of kidney stones. In a clinical trial of 25 people who underwent kidney stone removal surgery, a formulation containing 0.1 g D-mannose for 5 months reduced the formation of new stones [R].

2) D-Mannose Improves Congenital Disorders of Glycosylation

Congenital disorders of glycosylation result from genetic defects in enzymes that bind sugars such as D-mannose to proteins. The faulty, incomplete proteins can cause serious organ damage [R+].

Type Ib of this disorder is a rare defect in the enzyme that makes d-mannose from fructose. It can affect multiple organs such as the liver and brain, cause malnutrition, vomiting, and other serious symptoms [R+].

Intake of D-mannose can make up for the lack of normal D-mannose production. It resolved the main symptoms of this syndrome in multiple cases [R, R, R, R, R, R].

Type Ia of this disorder is caused by a defect in another enzyme in the D-mannose pathway. Although D-mannose supplementation corrected the defect in cells and mice, it has so far failed to improve the symptoms in humans [R, R, R, R, R].

3) D-Mannose Balances the Immune System (in animals and cells)

D-mannose helps build immune tolerance and may stabilize Th1/Th2/Th17 dominance. In cells, it activated Treg cells and increased their production, which is extremely important for balancing reducing all-around inflammation and autoimmunity [R].

A team of Chinese researchers recently caused a complete shift in thinking, claiming that D-mannose is a unique health-promoting substance. According to the above mentioned study, this simple sugar may be a safe dietary supplement to balance the immune system, treat and prevent autoimmune diseases and allergies [R].

Clinical trials have yet to prove the safety of D-mannose for reducing autoimmunity and inflammation, but moderate doses could probably achieve these effects. In animals, even a 9-fold increase in D-mannose blood levels didn’t cause side effects [R].

4) D-Mannose May Prevent Other Infections (in animals)

Clinical trials are required to test if D-mannose can help prevent infections from these disease-causing microbes in humans.

5) D-Mannose May Act as a Prebiotic (in animals)

Prebiotics are sugars that stimulate the growth of beneficial gut bacteria. D-mannose restored a healthy microbiome in mice with poor gut flora and reduced gut inflammation. In another study on obese mice fed on a high-fat diet, D-mannose favored the growth of the weight-loss-promoting gut microbes (Bacteroidetes) [R, R].

6) D-Mannose May Help with Weight Loss (in animals)

In obese mice fed a high-fat diet, D-mannose reduced weight gain, prevented diabetes and fat buildup in the liver. It also increased fat burning and reduced food absorption in the gut (so less calories are absorbed) [R].

Certain gut bacteria are linked to weight gain or weight loss. D-mannose shifted the microbiome composition to enhance weight-loss-promoting gut microbes called Bacteroidetes. It did so at the expense of another strain of bacteria linked to weight gain and obesity in humans (Firmicutes) [R].

D-Mannose Side Effects

D-mannose is generally well tolerated. At the doses used to prevent urinary tract infections, most studies found no side effects and only one reported mild diarrhea in 7.8% of people [R+].

The doses used for congenital disorder of glycosylation type Ib are much higher and the following adverse effects have been reported:

However, the effects were only seen in people exceeding the highest recommended dose of 1.2g/kg/day. This would amount to a very large dose of over 70g/day for a person of about 120 lbs.

D-Mannose Safety and Toxicity

In a child with congenital disorder of glycosylation type Ib, the injection of extremely high D-mannose doses for 3 weeks still didn’t cause any toxicity. Even the high doses typically used for this genetic disorder didn’t cause any damage in the long term (up to 10 years) [R, R, R+, R+].

It’s important to note that no clinical studies have evaluated its safety during pregnancy and breastfeeding. Additionally, high D-mannose doses caused reduced growth, blindness, organ malformations, and increased death rates in mouse and rat embryos. Pregnant and breastfeeding women should be cautious with D-mannose [R, R, R, R, R, R].

D-mannose is eliminated through urine and high blood levels are linked to an increased risk of kidney problems, which raised some concerns about long-term use. However, no cases of kidney damage have been reported with the typical doses [R+, R, R].

Drug Interactions

The antibiotic for fungal infections pradimicin A binds to D-mannose. D-mannose supplements can reduce the availability and effects of this antibiotic [R].

For Glycosylation Disorders

The D-mannose dose in people with congenital disorder of glycosylation type Ib is 0.1-0.2 g/kg up to 4-6x/day, while monitoring blood D-mannose levels [R, R+].

For Cats and Dogs

Some people buy D-mannose supplements for their pets. Analyses reported the use of D-mannose for urinary tract infections in cats and dogs with good results and without any adverse effects [R+].

The human dosage can be adapted to pets based on their weight. Large dogs would probably need a dose similar to what’s used in humans, while smaller cats and dogs would require only ¼ or less (depending on their size). Check with your vet if you’re unsure.

D-Mannose Reviews & User Experiences

A lot of women take D-mannose as an alternative to antibiotics for recurrent urinary tract infections. Almost all of them reported a reduced frequency of infections, improvement of the symptoms, and absence of adverse effects. Users who rated D-mannose lower usually complained about its high price and only a few reported occasional infections despite the therapy.

Most women with active urinary tract infections were gratefully surprised to start seeing positive results after only 1-2 days, while only a few complained that the product didn’t work for them.

Loose stools and bloating were the most commonly reported adverse effects.

Limitations and Caveats

Although the results on the use of D-mannose for urinary tract infections are very promising, they are based on only a few clinical trials. Additional studies with more people are required to confirm D-mannose as a practical, safe, and effective alternative to antibiotics.

Among the studies on D-mannose use for urinary tract infections, one was funded by the manufacturer of a D-mannose formulation (Probiotica SpA) and another one was carried out by two scientists working for another manufacturer (Deakos) [R+, R+].

Because congenital disorder of glycosylation type Ib is a very rare disease (less than 50 cases reported), the benefits and potential adverse effects of D-mannose therapy have only been investigated in a few case studies [R+].

The potential application of D-mannose in inflammatory conditions, infectious diseases other than UTIs, microbiome restoration, and weight loss have only been investigated in animals and cells. Clinical trials in humans are required to confirm these health benefits.

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.

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JOE COHEN

CEO, SelfHacked

About Joe

Growing up, Joe was plagued with a myriad of health issues such as gut problems, autoimmune issues, chronic fatigue, brain fog, insomnia, and general inflammation. Both conventional and alternative doctors weren’t able to help him, so he decided to fix himself. With lots of health questions and few satisfying answers, Joe decided to read every research paper he could get his hands on and conduct thousands of experiments on his own body in order to fix his health issues. Joe started SelfHacked in late 2013 when he successfully fixed all of his issues, and now it gets millions of readers a month looking to educate themselves about how they can improve their health. Joe is now a thriving author, speaker, and serial entrepreneur, founding SelfDecode & LabTestAnalyzer.

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